Android Question Land Survey

amaxco · May 13, 2021

Hello B4X community,

I appreciate your contribution and dedication which pumps livelihood in this wonderful development suite, thank you @Erel, the founder, you the generous enthusiasts.

Years before I purchased a rugged tablet, images attached, for benevolent purpose to help collecting data pertaining to the refugees pouring into as well as those been displaced within my home country Sudan.

Unfortunately, due to lack of developers and operators I preferred not to put it in use as prototype. But now I am thinking if it is possible to use it for the another purposes and if it works then I can confidently go ahead for other implementations.

At my home village we never had experienced land disputes because of the fact that earlier generations were peaceful and had not aspiration for any need other than living in harmony and working together for modest daily needs. But, recent generations have different thinking and thereby looking selfishly for their individual interests that is leading to disputes over land. Sadly, the politicians and government are busy with their own similar interest, though at bigger scale.

For me and other volunteers, hopefully initiating, we think we cam help by at least defining and documenting land property within the community knowledge in order to minimize disputes and thereafter help official concerned party by providing acquired information.

So, I want to ask your advice with regard to feasibility of using the subject device to perform land survey and other mapping as follows:

1. Connecting a GNSS receiver module like Matek Systems GNSS M9N-5883
2. Using MapIt software

I appreciate your advises and insights.

N.B. I have a copy of the device SDK.

@Erel please relocate this thread where you see appropriate

Brian Dean · May 14, 2021

I don't like to see questions on the forum go unanswered. You were well down Page 2 without a reply - at least I can give you another chance on Page 1.

I have looked at the Matek M9N-5883, which appears to be a flight-controller for a drone. How do you plan to interface that with your Android device? It might be worth putting a question on the B4R forum - somebody might have used this device with an Arduino.

How accurate do you need your GPS positioning to be? GPS mapping usually involves fixed ground reference stations to reduce error - without that positions can vary by two or three metres. This might not be a problem if you are working with large enough areas, but if you are trying to resolve disputes over individual dwellings then it could lead to more problems.

If you can, try to ask a more specific question, then perhaps people will find it easier to respond.

amaxco · May 14, 2021

Brian Dean said:
I don't like to see questions on the forum go unanswered. You were well down Page 2 without a reply - at least I can give you another chance on Page 1.

I have looked at the Matek M9N-5883, which appears to be a flight-controller for a drone. How do you plan to interface that with your Android device? It might be worth putting a question on the B4R forum - somebody might have used this device with an Arduino.

How accurate do you need your GPS positioning to be? GPS mapping usually involves fixed ground reference stations to reduce error - without that positions can vary by two or three metres. This might not be a problem if you are working with large enough areas, but if you are trying to resolve disputes over individual dwellings then it could lead to more problems.

If you can, try to ask a more specific question, then perhaps people will find it easier to respond.

Dear Brian,

Thank you for your reply.

Your point about no one is answering is important; I wish any one had commented that they do not understand one line of what I wrote ...

I will comment on your reply starting from the last sentence; If truly I am familiar with what I am asking I would not have spent time writing all these words! It was my best effort to try explaining what I want. Nevertheless, I think I explained the goal which is to use the device, that I have with me for long time, for other purpose we are in need now. Besides, I did not stick to the device but rather the need and for that I asked advice too. My simple understanding about the GNSS module is that it is used for determining locations which I need to define coordinates on the ground.

However, my simple question, forgetting about the device that I have, what is the most affordable portable land survey device with accuracy in the range of 20-50cm?

Brian Dean · May 14, 2021

I have worked with digital mapping for many years, but have not been directly involved with data collection, so I am not an expert.

Anything better than one metre accuracy is regarded as "high precision" so if you want to get down to around 50-20 cms then you are in that region. A company that I work with (in the UK) sells a 1.5m accuracy Android device for £1295. Measurements to this precision are going to need specialist devices with prices to match.

I have often wondered whether taking a GPS reading every 30 seconds for an hour and averaging the results would produce an accurate position. I have just found a report which suggests that that is not a simple solution, but it is something that you could experiment with. Here is a link. There might be other examples or ideas on the Web that you could try, and other forums.

Averaging GPS samples to improve accuracy

amaxco · May 14, 2021

Brian Dean said:
I have worked with digital mapping for many years, but have not been directly involved with data collection, so I am not an expert.

Anything better than one metre accuracy is regarded as "high precision" so if you want to get down to around 50-20 cms then you are in that region. A company that I work with (in the UK) sells a 1.5m accuracy Android device for £1295. Measurements to this precision are going to need specialist devices with prices to match.

I have often wondered whether taking a GPS reading every 30 seconds for an hour and averaging the results would produce an accurate position. I have just found a report which suggests that that is not a simple solution, but it is something that you could experiment with. Here is a link. There might be other examples or ideas on the Web that you could try, and other forums.

Averaging GPS samples to improve accuracy

Thank you so much dear Brian!

I will checkout and revert.

knutf · May 14, 2021

To get good enough accuracy for land survey I think you must use RTK ( Real Time Kinematic ) or PPK (Post-Processed Kinematic). In RTK and PPK you must have a Base (GPS with known position) and a Rover (GPS at the position where you do the survey)

For RTK you must have communication between Base and Rover, You get the position immediately
For PPK you log data in both Rover side and Base side. Then you process the data afterwards to get position.

This kit is suitable for range between base and rover up to 8km

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